Audio amplifiers, such as Class-D amplifiers, have a supply voltage for internal control circuits of the amplifier and a separate power supply input for the output of the amplifier. Such amplifiers suffer from inefficiencies caused by power dissipation which can be represented by the formula P=FNCV2, where P represents power dissipated, F represents frequency, N represents the number of transistors, C represents capacitance, and V represents the voltage. As exemplified by this formula, reducing the voltage to the amplifier would exponentially reduce the amount of power dissipated which in turn would increase the amplifier's efficiency.
But reducing voltage supplied to the amplifier necessarily reduces the performance of the amplifier since the amount of power provided to the amplifier is correspondingly reduced. Merely indiscriminately reducing the voltage without consideration of other factors associated with a playback device in which the amplifier is implemented and/or the content being played would significantly degrade the user experience while content is output through the amplifier.